The primary goal of this project is to determine if the presence of substantial abuse is associated with differential patterns of sustained neuropsychiatric disorders in mild traumatic brain injury (MTBI) patients. Traumatic brain injury (TBI) represents a major pubic health concern in the United States and worldwide. Neurocognitive and neuropsychiatric sequelae secondary to MTBI usually resolve within 90 days, however, for a significant minority of patients symptoms persist and can be severe. Incidence estimates of TBI based on U.S. studies are about 200 per 100,000 per year, thus yielding approximately 470,000 cases of brain injury annually. The most common causes of TBI include motor vehicle accidents, falls, assaults, firearm injuries, and sports. The majority of TBI is classified as mild. Toxicology studies of TBI patients reveal that they were often under the influence at the time of their acquired brain traumas. However, importantly, the relative contribution of acquired brain trauma versus substance-induced persistent neuropsychiatric pathology is incompletely understood. Understanding differential patterns of neuropsychiatric outcomes in minority patients is particularly important, because of the increased prevalence of intentional and unintentional injuries in the groups. Due to a dramatic surge in alcohol and other drugs in the past decade, there is a pressing need to study the associated neuropsychiatric aspects, particularly when substance abuse is combined with acquired brain trauma. It is now well-established that substance abuse, especially the abuse of alcohol and stimulants, can lead to hypertensive encephalopathy and ischemic brain hemorrhage, and that depression and other neuropsychiatric symptomatology are common (Bigler, 2001; Pulse Watch, 2000; Strickland, et al., 1998). Despite that alcohol and stimulants can induce significant cerebral pathology, little is known about differences in the magnitude of neuropsychiatric impairment, duration of symptoms, or the specific brain region(s) adversely impacted when substance abuse co-occurs with MTBI. Existing information is even less complete regarding differences in neurobehavioral outcomes secondary to ethnic, cultural, and socioeconomic influences. To strengthen our understanding of differences in neuropsychiatric and quality of life (QOL) outcomes in MTBI patients, this proposed project utilizes a five-year, between- and within-subject, repeated-measures design to investigate these parameters in a sample of 200 subjects. Fifty MTBI subjects positive for substance abuse will be evaluated within thirty days of injury (Time 1), and three months later (Time 2). Fifty non-MBTI and non-substance abusing subjects will be evaluated (Time 1), and three months later (Time 2). The proposed study has the following specific aims: 1. To determine if severity and duration of neuropsychiatric impairment in MTBI is associated with the presence of substance abuse. 2. To compare severity of neuropsychiatric and neuropsychological functioning between MTBI and substance abuse subjects over time (three months after initial assessment). 3. To identify and describe factors that are associated with improvement in neuropsychiatric symptoms via evaluation of primary or secondary analyses (such as interventions, demographics, or socioeconomics).